The present invention relates to reactors used in semiconductor processing and more particularly to the acceleration of a plasma etching process with a reliable elevated temperature control so as to reduce the likelihood of substrate damage.
Typically, semiconductor devices are manufactured by using combinations of differing layers of conductive, insulating, and semiconducting materials. It is often necessary to form openings in an upper substrate layer on a wafer so that contact can be made with an underlying substrate layer. To accomplish this, a mask is deposited on the substrate. The mask is patterned to cover selected regions while leaving other regions exposed. The wafer is then subjected to a corrosive type of environment which will etch the exposed portion of the substrate. However, the etching materials also tend to etch the masks. It has been an ongoing objective of the industry to develop etching methods and apparatus which will selectively etch substrates on a cost effective basis.
Dry etchers use gas which forms a plasma to etch the substrate. Dry etching techniques are often referred to as reactive ion etching or plasma etching. In the prior art types of dry etchers, a plasma is formed by injecting a gas into an area between two electrodes. The reaction of the gas to the RF field produces a plasma which generates ions. The ions then collide with the substrates causing portions of the surface of the substrate to etch, or chip, off.
In the prior art etchers, the chemical reaction rates are frequently unacceptably low. With elevated temperatures, the reaction rate is increased, but control is not sufficiently precise to reliably produce acceptable products. Efficient use of the apparatus with a variety of different semiconductor materials is a continuing goal. Control of substrate temperature by using a prior art temperature controlled water recirculation unit is limited to temperatures less than 100.degree. C., which is too low for many substrate materials. Elevating the substrate temperature by reliance on plasma or other radiation heating as in the prior art is unreliable due to lack of temperature regulation.